In recent years, the importance of security in cloud services has been widely recognized. A proposed service, for example, stores data encrypted by homomorphic encryption schemes in a database in a cloud network (hereinafter simply referred to as a cloud), performs statistical processing on encrypted data stored in the database without decrypting the encrypted data to generate encrypted data representative of the result of processing, and acquires as needed the encrypted data representative of the processing result to decrypt the encrypted data.
As a technology related to the above service, homomorphic encryption schemes is described, for instance, in Non-Patent Literature 1.